Essential Arms lower rx $66.00 plus shipping ($8) FFL transfer $20 = $94
(Stinger, Mega, Double Star forged lowers about $20 more)
J&T Rifle or Carbine kit $450 + $20 shipping = $470
(opt, add chrome lined barrel, extra $50)
$564.00
The J&T kits have excellent parts, and the upper receiver/barrel assembly is completely assembled and ready to go, so no need to buy barrel wrench, action block, etc.
Not $550, but real close.